The Original Slide Rule Replacement - Hewlett Packard Handheld Scientific Calculator

As I have pointed out in a previous post, I am a calculator collector.  As I was doing research about HP Calculators in order to replace the one used during my college years, I learned of the original handheld scientific calculator.  This was invented by HP in the early 70s.  At first the machine didn't even have a model name, it was just the HP Handheld Calculator, but later it was labelled as the HP 35 since it had 35 keys on it.

As of this writing in early 2025 prices for the original HP 35 are rising with good working examples going for several hundred dollars on eBay.  These are much more repairable than modern calculators and there is at least one detailed tutorial video showing the process to take them apart and clean them.  The repairability and information online made me feel comfortable enough to purchase a non-working unit on eBay and attempt a repair myself, but things are often more complicated than initially expected.

The unit arrived and I was able to take it apart as shown in the video.  There were signs that this one had already been taken apart, which was disappointing since that was not shown in the eBay listing.  I should have asked for pictures of the back.  Cleaning the contacts did not resolve the dead keys on this calculator as it did in the YouTube video so it turns out that this calculator had something wrong with the electronics on the main circuit board.  I reflowed the solder joints and poked around on the main board a bit, it isn't very complicated, but I'm guessing one of the custom logic ICs is damaged, so this project went on hold for a few weeks.

Shortly after I got an email from one of my saved searches on eBay.  It was the cheapest HP35 on eBay in. quite a while.  It was a loose calculator without a Power Supply.  I talked to the seller and he had no way to power it up, so it was a gamble, but he also showed the back of the unit and this one had not been opened, so I took the chance and purchased it.

The second calculator was in really rough shape.  When I got it on the workbench it had battery corrosion on the inside of the battery compartment and it wouldn't power up.  I started disassembly, cleaning as I went.  It was obvious that corrosion had gotten inside and affected the power circuits under the battery compartment, however, the design was modular and that was not a part of the main logic board that was bad on the other calculator, so I was still hopeful.

When I swapped the older logic board onto the newer HP35 it fired right up and worked!  I was very happy to have a working calculator after buying two broken ones.  As soon as I got one working I checked for the 2.02 bug.  The working Logic Board is from the first year, 1972, but it does not have the bug, which is OK with me since it would have looked out of place in the newer case with the H P 35 logo on the front.

I also rebuilt the battery pack with 3 NiCd AA cells and it looks quite nice running without being plugged in...

So now that I have the first ever scientific calculator, the HP 35, and my favorite calculator, the HP48G that got me through college.  These are the bookends for my collection and should not really need any more calculators in the collection.  For now.

Another Beige Alpha Joins the Fleet - Compaq Professional Workstation XP1000

In the middle of last year an interesting workstation computer came up for sale on Facebook Marketplace here in my area.  The Compaq Professional Workstation XP1000 is an Alpha based workstation from just after Compaq purchased Digital Equipment Corporation.  The Facebook Markeplace ad stated that it was stopping on a boot screen and that it might not be working, but the price was low enough that I thought it was worth the risk of not being able to repair it.

Once I got the system home I was able to verify that the system was in the condition described and then started to read what I could find about this computer.  I soon discovered that the motherboard had a password installed on it.  In the PC world we would call this a BIOS password, but for an Alpha machine like this, it's the SRM console password.  The SRM console uses a command line but with it locked out even the help command was generating an error "Console is secure.  Please login.".  Because PCs have a jumper to reset this I was quite hopeful that it would just be a matter of time till I figured out how to reset that password but after not finding much documentation online I decided to ask for help on the Vintage Computer Federation Forums.

As usual there were several people who were a big help there, including one gentleman that uploaded some documentation to the thread that I had not been able to find online anywhere else.  Sadly, though, we did NOT discover a backdoor designed by Compaq to reset the console password.  Although I could not find an explicit statement for this motherboard I did learn that were other machines designed by Compaq that did not contain a back door, if the password is lost, the main logic board containing the firmware must be replaced.  So I decided to put the project on hold and keep the machine.  I setup a saved search on eBay since you never know what will pop up there and didn't think much about this project in the second half of last year.

At the end of last year I gave quite a bit of thought to my Vintage Computing hobby.  I purged alot of my project machines, selling, donating to Free Geek, or recycling responsibly.  I also went through my wish lists and eBay saved searches and purged items that were no longer of interest and I discovered that I had setup the wrong search, adding an extra zero.  When I fixed the saved search I was shocked to learn that there was a logic board on eBay for sale!  I watched the item for a while and eventually made an offer that was accepted.

The board shipped from Israel so it took a while to get here but once it arrived I was able to pull my machine completely apart.  I used this as an opportunity to do some much needed dusting inside the case of this machine.  It was a huge relief when the system started back up after re-assembly and an even bigger relief when I was able to use the SRM console and issue commands to boot an Operating System off an Installation Disk!

Once I could start to explore, I learned that this was one of the newer XP1000 machines.  This machine can run the VMS operating systems and Unix like systems, but not Windows NT.  The older, slower machines could boot NT, but I already have one Alpha machine setup that way.  I know at least one DEC hardware enthusiast  who will be glad to see the machine running DEC software and not Microsoft software.

I had some old media for OpenVMS which I had burned while I was a part of the Community Licensing program, but that program has ended now.  I was able to install OpenVMS 8 on the hardware, but without licenses it's not very interesting or useful.  After searching on the Internet and reading for a bit, I learned that the archived version of Tru64 Unix on WinWorld has keys with the archive, so I gave that a try, and it worked well.

Configuring networking was a bit of a challenge, but I ended up getting that working with a Static IP and now the computer can read articles on FrogFind.com and 68k.news just fine.  I'm quite happy with how the machine turned out...

I was disappointed that I couldn't load older software on here.  I have been looking for some VAX hardware since that is what we used back in College, I remember the Motif Window Manager and that was such an interesting look and feel, but I didn't know that Motif was the precursor to the Common Desktop Environment (CDE).  Because of multiple vendors working together on this more open code base this Compaq (Digital Equipment) machine will join several others CDE machines that I have including IBM AIX, Sun Solaris, and SGI Irix.

I am not a calculator collector, I am not a calculator collector.

I am not a calculator collector.  I have to keep saying this to myself because I don't need another genre of items to collect, but I'm quite tempted by this since it is adjacent to retro computing.  I've managed to avoid printers (mostly), typewriters completely, and vintage test equipment, among many other interesting items that I would collect if time money and storage space were not limited.

So I have a few calculators.  I purchased a Radio Shack Pocket Computer 4 off Facebook Marketplace in 2020...

And since then I've been picking up interesting, older calculators from the 70s and 80s at Garage Sales and Thrift Shops when I can find them including a couple of hand held Casio units.  My parents had a Casio on their desk, it had a mesmerizing Nixie tube display and so although it was "portable / battery powered" it stayed plugged in and on the desk.  The Calculator Wars of the 70s were historically significant to the development of home computing as they occurred right before the home computer revolution and included many of the same companies.  Calculators were the "killer app" of Microprocessors before the home computer revolution began, but this is well covered elsewhere.

My personal calculator history started with my first graphing calculator, a TI-81.  My parents bought this for me while I was in high school and I spent quite a bit of time puttering with it and even wrote some simple programs to run on it.  I was recently able to reacquire a TI-81 from Free Geek Twin Cities and add that to my calculator not-a-collection.

My favorite calculator is the HP48G which got me through engineering school.  Back in the day we didn't have laptop computers for every student so pretty much everyone had an HP 48 of some sort.  It was hard to learn how to use it, but once I'd gotten the hang of it I can always come back to an RPN calculator, just like riding a bicycle, you never really forget how.  There's a review video from Calculator Culture on YouTube that I'd recommend, it has helped me understand why this calculator is so unique.

I wore out my initial 48G calculator.  I had tried to repair it at one point, but it was not designed for service and I ended up breaking mine.  I missed having it enough that about ten years ago I had purchased an HP50G calculator hoping that it would replace my worn out calculator, but I didn't like using it as much.  Another Calculator Culture review video explains this calculator well.  I ended up selling my HP50G as it didn't really match my expectations and was different enough from the 48 that is just didn't feel the same.

So after watching a few videos from HPcalc.org's recent conference and the Calculator Culture videos I realized that the best way to "Scratch the Itch" so to speak would be to just go ahead and buy an original HP48G.  With my new knowledge about the hardware revisions and the typical problems, I was hoping I could find a nice one on eBay at a reasonable price, and after waiting and shopping for a couple of weeks, I was able to find this lovely unit here...

I've paired it with the original manual set that I'd kept all these years.  I'm glad I kept the manual since there's alot I've forgotten about how to use the machine (the manual is hundreds of pages long).  As described in the review video above the LCD screen isn't great, the contrast is poor, although not being backlit means that the battery life is quite good.  The keyboard is amazing, the keys are clicky, very tactile and enjoyable to use.

I've enjoyed having this machine back at my desk, and I'm getting back into the habit of using it.  During my research I've also found a much more modern iOS app that emulates the 48.  I've used about a half dozen of these over the years since getting my first Smart Phone and this one is the most useful and stable, it's called iHP48 and it is much better than other iOS Apps that emulate HP 48 which I have used before.  This is the main calculator app on my phone now and I use it almost daily.

Doing the research about HP 48 and being exposed to other calculator collectors has helped me learn about the history and development of the handheld scientific calculator.  I've become aware of the first Handheld Scientific Calculator, the HP 35 from 1972.  But this is a story for another day, so I will wrap up this bLog post by simply stating the obvious, I am a calculator collector.

My Newest, Oldest Apple II Plus (1979)

There were three very important home computers that came out in 1977, the Commodore PET, the Apple II and the Radio Shack TRS-80 Computers.  We retroactively call the Radio Shack the TRS-80 Model 1 but that is not how it was advertised at the time.  Also, the use of the term trinity to describe these three computers is something that appears to have begun in the mid 90s.

One of my goals in the Retro Computing hobby is to own all three of the original premade personal computers that didn't have to be built from kits like the Altair 8800.  So far I have been able to acquire; an Apple II Plus from 1979, a Commodore PET 4016 from 1980, and an original TRS-80 Model 1 computer.

Recently on a trip to Free Geek Twin Cities I was able to acquire another Apple II Plus machine and this turned out to be a machine from 1979.  This got me thinking again about wanting to get as close as possible to an original Apple II experience from 1977 and so I started doing research.  Tech Time Traveller has a really helpful video on this topic here.  He also painnstakingly built up this list of machines have have sold on eBay, since eBay doesn't keep pricing information and old listings around on their site very long  Thanks Tech Time Traveller!  Now that I know an original Apple II from eBay is probably more than I want to spend right now, what are my options?

Going back to the machine from  Free Geek, I learned that the board in my "newest" Apple II Plus is a "Revision 4" logic board.  This is from the period in 1979 was when Apple was making both the II and the II Plus at the same time, and often with the same logic board and only different ROMs and different RAM amounts.

At the same time as this was going on a listing came up on eBay for a computer that was listed as an original Apple II machine, but after inspecting it it seems likely that this machine had been upgraded to II Plus, which I later confirmed was the consensus in one of the Apple II Facebook groups.  I'm still considering the option of building an "Original Apple II" by getting bits and pieces and putting them together, but I think I'd rather hold out and wait till one comes along that is more complete locally, or with a backstory that I can learn about.

In the meantime, I learned about the Apple II ROM card, which was a period correct accessory card from 1979 that folks bought when they were upgrading their Apple IIs to Apple II Plus which allowed them to put the old ROMs onto an expansion board and switch them in at will from a switch on the back of the computer.  I used to have a modern card that did this, but ironically that card failed, so I set out to find a vintage card that still had the correct ROMs on it (Many, perhaps most of the ones on eBay have been stripped).  This article on the VCFed forums explains which ROMs where the period correct ones for an original Apple II (With Woz's Integer basic, and without Applesoft Basic).  I was able to find and acquire one of these period correct cards with the full ROM set, and it works great...

So, as of this writing, my Apple II Plus behaves in exactly the same way as the original machine, so I am now able to explore software from that era.  A good win for a reasonable price with parts that are still relatively inexpensive.